The present invention relates to a coupler for connecting reinforcing bars which is used for connecting reinforcing bars to each other that are used in a construction site and, more specifically, to a coupler for connecting reinforcing bars which has increased strength and excellent fastening force on reinforcing bars through a structural improvement, and also provides increased convenience in assembly, thereby maximizing the manufacturing efficiency. The present invention has increased strength and excellent fastening force on reinforcing bars through a structural improvement to a coupler body, and does not require a separate fixing means by allowing a plurality of piece bodies to be assembled to a piece body guide provided with a magnet, thereby providing increased convenience in assembly and maximizing the manufacturing efficiency.